1. Field of the Invention
The present invention relates to a pixel circuit, a display including the same, and a driving method thereof. More particularly, the present invention relates to a pixel circuit including a feedback feature, a display including the same, and a driving method thereof.
2. Description of the Related Art
Recently, various flat panel displays capable of reducing weight and volume, which are disadvantages of cathode ray tubes (CRTs), have been developed. Flat panel displays include, e.g., liquid crystal displays (LCDs), field emission displays (FEDs), plasma display panels (PDPs), and organic light emitting displays.
Among the flat panel displays, the organic light emitting displays may make use of organic light emitting diodes (OLEDs), which may emit light by re-combination of electrons and holes. The organic light emitting display may offer various advantages, e.g., high response speed and low power consumption.
A pixel of a conventional organic light emitting display may include an OLED and a pixel circuit. The pixel circuit may be coupled to a data line and a scan line, and may control the OLED. An anode electrode of the OLED may be coupled to the pixel circuit, and a cathode electrode thereof may be coupled to a power supply, e.g., ELVSS. The OLED may generate light of a predetermined luminance corresponding to an electric current provided by the pixel circuit. In particular, when a scan signal is supplied to the scan line, the pixel circuit may control the amount of an electric current provided to the OLED in correspondence with a data signal provided to the data line.
The pixel circuit may include first and second transistors and a storage capacitor. The first transistor may control an amount of an electric current flowing from a power supply ELVDD to the power supply ELVSS through an OLED according to a voltage charged in the storage capacitor, and the OLED may emit light corresponding to the amount of an electric current supplied from the first transistor. The second transistor may be coupled between the data line and the scan line. The second transistor coupled to the scan line and the data line may controllably provide a data signal from the data line to the storage capacitor, and the storage capacitor may be charged with a voltage corresponding to the data signal.
The above-described pixel circuit of the conventional organic light emitting display may not be entirely satisfactory, as a display including a plurality of such pixel circuits may not display an image of uniform luminance. In detail, threshold voltages of the drive transistors in the pixel circuits may be different depending on, e.g., fabrication process variations. When the threshold voltages of the drive transistors are different, the OLEDs in the display may emit light of differing luminances even though a data signal representing a same gradation is supplied to each of the pixel circuits.
One approach to overcoming such drawbacks is to provide a pixel circuit that includes threshold voltage compensation for the drive transistor. However, such threshold voltage compensation may require six or more transistors in each pixel circuit, as well as additional wiring for controlling the transistors. Moreover, when six or more transistors are included in the pixel circuit, the structure of the pixel circuit may become complex. Furthermore, the above-described threshold voltage compensation may not compensate for other factors such as the carrier mobility of the drive transistor.